Integrated position and direction system for determining position of offset feature

ABSTRACT

An integrated position and direction system is disclosed that includes a digital compass, wherein the digital compass includes at least three sensors, and a satellite positioning system (SATPOS) having a receiver adapted to receive satellite position determining signals. Direction is determined using the digital compass and heading is determined using the SATPOS. At a first location, the integrated position and direction system is oriented to the offset feature and is operated to determine a first set of measurements relative to the offset feature using the digital compass and the satellite positioning system. At a second location, the integrated position and direction system is oriented to the offset feature and is operated to determine a second set of measurements relative to the offset feature using the digital compass and the satellite positioning system. The integrated position and direction system calculates the position of the offset feature using the first and second sets of measurements.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of Ser. No. 09/614,392 Jul.12, 2000 which is a continuation-in-part of Ser. No. 09/546,236 Apr. 10,2000.

TECHNICAL FIELD

This invention relates to position determination systems. Specifically,the present invention relates to a method and apparatus for determiningposition of an offset feature.

BACKGROUND ART

Satellite positioning system (SATPOS) devices that determine positionusing the satellites of the US Global Positioning System (GPS) arecommonly used for navigation of vessels, vehicles, airplanes, and otherconveyances. SATPOS devices are also used for surveying, constructionsite planning and management, mining, oil and gas exploration anddevelopment, etc. Also, handheld SATPOS devices are used for personalnavigation, data collection, data maintenance, etc.

SATPOS devices are quite effective for indicating the position of theSATPOS device. Position is typically indicated using either analphanumeric indication of position or by displaying a map thatindicates position. Alphanumeric indications of position typicallyinclude coordinates such as, for example, Latitude and Longitude, WorldGeodetic Survey (WGS) Coordinates, etc.

Map displays typically indicate position by an icon or other indicatorvisible on a map. One such map display, typically referred to as amoving map display, displays the position of the SATPOS in the center ofthe displayed map. Such map displays typically are oriented such thatthe top of the SATPOS device's display indicates North (either magneticNorth or true North). That is, irrespective of the direction in whichthe SATPOS device is actually oriented, North is shown at the top of thedisplay. For users that intuitively know which direction is North, suchmaps are adequate for locating features displayed on the map. However,for users that do not know where North is, or when visibility isobscured such that the user cannot determine where North is, such mapsare inadequate for guiding the user to a destination or feature on themap.

For many commercial applications of SATPOS systems, such as constructionsite planning and management, surveying, navigation, etc., it isessential that an operator be able to locate features displayed on themap. Such users typically operate a separate device for indicatingdirection such as a conventional magnetic compass.

Some SATPOS devices indicate the direction of movement of the SATPOSdevice, typically referred to as “heading.” Typically, heading isdetermined by analysis of determined position in relation to priordeterminations of position as the SATPOS moves. Typically, SATPOSdevices that indicate heading use a map display oriented such that thetop of the SATPOS unit (e.g., the top of the unit's display) correspondsto North(either magnetic North or true North).

Some prior art SATPOS devices orient the displayed map such that the topof the SATPOS unit (e.g., the top of the unit's display) corresponds tothe direction of movement calculated by the SATPOS device. This gives agood approximation of the user's heading as long as the user continuesto move and as long as the SATPOS unit is oriented in the direction ofmovement, allowing a user to easily determine the location of featuresvisible on the display.

However, when the SATPOS device stops moving, determination of headingcan no longer be made. Some SATPOS systems maintain the previous headingfor orienting the moving map display for a given time interval. Otherprior art SATPOS systems default to positioning North at the top of themap. This can be quite confusing to the user.

Recently, digital compasses have been developed that can indicatedirection. However, digital compasses must be calibrated to properlyalign the digital compass prior to use. Also, each time that magneticenvironment around the compass changes, the digital compass must berecalibrated. Digital compasses are typically calibrated by moving thedigital compass in a full horizontal arc. The calibration process takestime and is prone to operator error. Also, calibration error can occuras a result of local magnetic anomalies.

Typically, extensive measuring equipment is utilized to determine theposition of an offset feature which is inaccessible or which isinconvenient to access. Time and resources are spent. Moreover, morethan one person is typically needed to accomplish the task.

What is needed is a method and apparatus for providing an accurateindication of heading to a user of a SATPOS device. Also, a method andapparatus is needed that meets the above needs and that accuratelyindicates direction when the SATPOS is not moving. Also, a method andapparatus is needed that is easy to use and that does not require a userto manually calibrate a compass. Also, a method and apparatus is neededthat facilitates determining position of an offset feature withoutsetting up extensive measuring equipment. The present invention meetsthe above needs.

DISCLOSURE OF THE INVENTION

The present invention provides a method and apparatus that accuratelyindicates direction and heading to a user of a satellite positioningsystem (SATPOS) device. The integrated position and direction system ofthe present invention includes a digital compass for indicatingdirection when the SATPOS is not accurately determining direction. Inone embodiment, the digital compass is comprised of at least threesensors.

An integrated position and direction system is disclosed that includes aSATPOS having a receiver adapted to receive satellite positiondetermining signals. The integrated position and direction system of thepresent invention also includes a digital compass that is adapted todetermine direction.

The integrated position and direction system also includes a controllerfor controlling the operations of the integrated position and directionsystem. The controller is coupled to the SATPOS, the digital compass,and to a display.

In one embodiment of the present invention, when the SATPOS is moving,the direction of movement or “heading” determined by the SATPOS isindicated on the display. When the SATPOS is not moving, the directiongiven by the digital compass is indicated on the display. Therefore,while the SATPOS is moving, the heading is indicated, and when theSATPOS is not moving, direction is indicated using the digital compass.Thus, the present invention provides a method and apparatus forproviding an accurate indication of both heading and direction to a userof a SATPOS device.

In one embodiment, the digital compass is automatically calibrated bythe SATPOS when the SATPOS is moving. This calibration can be initiatedby the user or can be fully automatic. More particularly, the digitalcompass of the present invention is calibrated automatically, either asa result of user input (e.g., selection of an icon, pressing of abutton, etc.), or as a result of user-defined criteria for automaticcalibration. That is, the user can program the present invention toautomatically calibrate the digital compass (e.g. when velocity exceedsa given threshold, whenever the SATPOS begins moving, periodically whilethe SATPOS is moving, when the difference between the SATPOS determinedheading differs from the heading indicated by the digital compass bymore than a predetermined threshold, etc.) Thus, the position anddirection system of the present invention is easy to use because therein no need for a user to calibrate a compass as is required using aprior art compass alone.

The present invention also provides a method and apparatus fordetermining position of an offset feature. In one embodiment, anintegrated position and direction system is described that includes adigital compass and a satellite positioning system, and which isoperable to determine the position of an offset feature.

In one embodiment, the integrated position and direction system isoriented so as to indicate the direction to the offset feature at afirst location and is operated to determine a first direction to theoffset feature relative to the first location using the digital compassand to determine a first position using the satellite positioningsystem.

The integrated position and direction system is moved and placed at adifferent location, referred to hereafter as a “second location”. At thesecond location, the integrated position and direction system isoriented so as to indicate the direction of the offset feature relativeto the second location and is operated (e.g., by pressing a button) todetermine a second direction to the offset feature using the digitalcompass and to determine a second position using the satellitepositioning system. The integrated position and direction systemcalculates the position of the offset feature using the first and seconddirections and the first and second positions.

These and other objects and advantages of the present invention will nodoubt become apparent to those of ordinary skill in the art after havingread the following detailed description of the preferred embodimentsthat are illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

FIG. 1 is a diagram of a position and direction system in accordancewith one embodiment of the present invention.

FIG. 2 is a diagram of an embodiment of the position and directionsystem of FIG. 1 in accordance with one embodiment of the presentclaimed invention.

FIG. 3 is a perspective view of an embodiment of the position anddirection system of FIG. 2 in accordance with one embodiment of thepresent claimed invention.

FIG. 4 is a diagram of a position and direction system in accordancewith one embodiment of the present claimed invention.

FIG. 5 is a flow chart illustrating a method for indicating directionand heading in accordance with one embodiment of the present invention.

FIG. 6A is a diagram showing an exemplary display that indicatesposition and heading in accordance with one embodiment of the presentclaimed invention.

FIG. 6B is a diagram showing an exemplary display that indicatesposition and direction in accordance with one embodiment of the presentclaimed invention.

FIG. 7A is a diagram showing an exemplary display that indicatesposition and heading in accordance with one embodiment of the presentclaimed invention.

FIG. 7B is a diagram showing an exemplary display that indicatesposition and direction in accordance with one embodiment of the presentclaimed invention.

FIG. 8A is a diagram showing an exemplary display that indicatesposition and heading in accordance with one embodiment of the presentclaimed invention.

FIG. 8B is a diagram showing an exemplary display that indicatesposition and direction in accordance with one embodiment of the presentclaimed invention.

FIG. 9A is a diagram showing an exemplary display that indicatesposition and heading in accordance with one embodiment of the presentclaimed invention.

FIG. 9B is a diagram showing an exemplary display that indicatesposition and direction in accordance with one embodiment of the presentclaimed invention.

FIG. 10 is a flow chart illustrating a method for calibrating a digitalcompass in accordance with one embodiment of the present invention.

FIG. 11 is a schematic representation of an exemplary configuration fora 3-Sensor magnetic sensor in accordance with one embodiment of thepresent claimed invention.

FIG. 12 is a perspective view of an integrated position and directionsystem 100 in accordance with an embodiment of the present inventionthat includes a visual alignment mechanism 90.

FIG. 13 is a flow chart illustrating a method 1500 of determiningposition of an offset feature 930 in accordance with an embodiment ofthe present invention

FIG. 14 shows an exemplary diagram in which an integrated position anddirection system is located at a first location (L1) and subsequentlylocated at a second location (L2) for determining the location of offsetfeature 930.

FIGS. 15A-15G illustrate exemplary angles and distances that can be usedto calculate the position of the offset feature 930 in accordance withan embodiment of the present invention.

FIG. 16 shows an exemplary diagram in which an integrated position anddirection system is located at a first location (L1) and subsequentlylocated at a second location (L2) and subsequently moved to a thirdlocation (L3) for determining the location of offset feature.

FIG. 17 illustrates an embodiment that includes a graphical userinterface that is used for determining the position of an offsetfeature.

The drawings referred to in this description should be understood as notbeing drawn to scale except if specifically noted.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone of ordinary skill in the art that the present invention may bepracticed without these specific details. In other instances, well knownmethods, procedures, components, and circuits have not been described indetail as to not unnecessarily obscure aspects of the present invention.

FIG. 1 is a logical representation of components of integrated positionand direction system 100 in accordance with one embodiment of thepresent invention. Integrated position and direction system 100 includesSatellite Positioning System (SATPOS) 3 that is operable for determiningposition. In one embodiment, SATPOS 3 is adapted to determine positionusing a Satellite Positioning System such as the U.S. Global PositioningSystem (GPS).

In operation, SATPOS 3 determines the location of SATPOS 3 by analysisof satellite position determining signals such as signals fromsatellites of the U.S. GPS. Position signal processing circuitry inSATPOS 3 also determines the direction of movement of SATPOS 3, referredto hereinafter as “heading” and couples the determined heading tocontroller 1. In the present embodiment, heading is determined bycomparing satellite position determining signals received as theintegrated position and direction system 100 moves.

Integrated position and direction system 100 of FIG. 1 also includesdigital compass 4. Digital compass 4 is operable to determine directionand couple direction to controller 1. More particularly, in the presentembodiment, digital compass 4 determines the compass direction thatcorresponds to the orientation of the integrated position and directionsystem 100.

Continuing with FIG. 1, controller 1 controls the operation ofintegrated position and direction system 100. In one embodiment,controller 1 is a general-purpose computer. Alternatively, controller 1is an integrated circuit device such as a microcontroller or anApplication Specific Integrated Circuit (ASIC) device or a FieldProgrammable Gate Array (FPGA) device. In one embodiment, the functionsof controller 1 are performed by a general purpose microprocessor thatis operable to execute instructions contained in one or more softwareprogram(s).

In the present embodiment, controller 1 is operable to display thedetermined position and the determined direction and/or heading ondisplay 2. Display device 2 may be a liquid crystal device, flat paneldisplay, or other display device suitable for creating graphic imagesand alphanumeric characters recognizable to the user.

FIGS. 2-3 show an embodiment of the present invention that isincorporated into a handheld portable housing. That is, the housing issmall enough to fit into a user's hand.

Referring now to FIG. 2, integrated position and direction system 200 isshown to include SATPOS 3 that is operable for determining position. Inthe present embodiment, SATPOS 3 includes SATPOS antenna 10, SATPOSreceiver 11, and SATPOS processor 12. In one embodiment, SATPOSprocessor 12 is a GPS processor made by Trimble Navigation, Ltd. ofSunnyvale, Calif. In this embodiment, SATPOS antenna 10 is an ACE IIGPS™ antenna, manufactured by Trimble Navigation, Ltd. and SATPOSreceiver 11 includes a SIERRA GPS™ chipset, manufactured by TrimbleNavigation, Ltd. Although such a specific implementation is described,the present invention is also well suited to an embodiment havingvarious other components and features.

Referring still to FIG. 2, microprocessor 20, in conjunction withdirection program 22 perform the functions of controller 1 of FIG. 1.That is, in the present embodiment, direction program 22, operable onmicroprocessor 20 controls the operations of integrated position anddirection system 200. In the present embodiment, microprocessor 20 is ageneral-purpose microprocessor that has low power consumption such as,for example, a Motorola RISC microprocessor made by Motorola Inc., ofAustin, Tex. Alternatively, other types of processors, an ASIC device ora FPGA device can be used.

Continuing with FIG. 2, power source 24 provides power to the variouscomponents of integrated position and direction system 200. Power source24 may be any suitable power source that is light-weight and compactsuch as, for example, built-in rechargeable batteries, AA batteries orAAA batteries.

Data storage device 25 is coupled to controller 20 and is adapted tostore data. Data that can be stored in data storage device 25 includes,for example, an operating software program such as direction program 22.Data storage device 25 may be any type of digital data storage medium.In one embodiment, data storage device 25 is a Random Access Memory(RAM) device such as, for example, a Static Random Access Memory (SRAM)device, a Dynamic Random Access Memory (DRAM) device. Alternatively,other types of memory storage devices such as flash memory, tape, CDROM, or DVD may be used.

Referring still to FIG. 2, connection mechanism 21 is coupled tomicroprocessor 20 and is adapted to connect to external devices such as,for example external computers. This allows for easily and quicklydownloading new programs for operation on microprocessor 20 and allowsfor updating direction program 22. In one embodiment, connectionmechanism 21 is a connector that complies with the RS-232 standard.

With reference again to FIG. 2, display device 28 is also electricallycoupled to microprocessor 20. In one embodiment, display device 20 is anactive matrix liquid crystal display. Alternatively a cathode ray tube,or other display device suitable for creating graphic images andalphanumeric characters recognizable to the user can be used.

Input device 27 is coupled to microprocessor 20 and allows for couplinguser input to microprocessor 20. In the present embodiment, input device27 includes function keys and an alphanumeric keypad. Alternatively,input device 27 includes a trackball, mouse, touch pad, joystick. Thepresent invention is also well suited to receiving user input by othermeans such as, for example, voice commands.

Referring now to FIG. 3, an embodiment of position and direction system200 is shown that is incorporated into housing 30 that is small enoughto hold in a user's hand. In the present embodiment, function keys 32and alphanumeric keypad 33 allow for coupling user input to position anddirection system 200. In one embodiment, one or more of function keys 32operates as a cursor control device. That is, one or more of functionkeys 32 allows the computer user to dynamically signal thetwo-dimensional movement of a visible symbol (cursor) on the displayscreen of display device 28.

FIG. 4 shows an embodiment of the present invention in which SATPOSprocessor 12 is used for controlling the operations of the integratedposition and direction system 400. Because SATPOS processor 12 is usedfor controlling the operations of integrated position and directionsystem 400, there is no need for a second microprocessor such asmicroprocessor 20 of FIG. 2.

In the embodiment shown in FIG. 4, SATPOS processor 12 is operable todetermine position and heading using SATPOS signals and is also operableto receive direction determined by digital compass 4. In thisembodiment, SATPOS processor 12 includes instructions for determiningwhich source of direction signals (heading from SATPOS signals ordirection determined by digital compass 4) is to be indicated (e.g.,displayed) on display device 28. In the present embodiment, theseinstructions are contained in direction program 42 that controls theoperations of integrated position and direction system 400. Directionprogram 42 is a computer program that is operable on SATPOS processor12. However, alternatively, instructions necessary for the operation ofintegrated position and direction system 400 can be implemented on anASIC, a FPGA, or similar device.

In the present embodiment, position is indicated on display device 28.In one embodiment, position is indicated alphanumerically using latitudeand longitude. Alternatively, position is indicated by an icon displayedon a moving map display.

In the present embodiment, reference to a satellite positiondetermination system, or “SATPOS” herein refers to a Global PositioningSystem (GPS), to a Global Orbiting Satellite System (GLONASS), to ahybrid system that is capable of using satellites from the GPS and theGLONASS, and to any other positioning system, including pseudolites,that provide signals that can be used to determine position. The term“satellite position determination system” and “SATPOS” as used herein,is intended to include position determination using pseudolites orequivalents of pseudolites, and the term “satellite positiondetermination system signals” and “SATPOS signals,” as used herein, isintended to include position determination system-like signals and datafrom pseudolites or equivalents of pseudolites. Also, signals from othersources such as LORAN, Wide Area Augmentation System (WAAS) satellites,etc. may be used to determine position.

In the embodiments shown in FIGS. 1-4, digital compass 4 is used todetermine direction. In the present embodiment, digital compass 4 is acompass that determines direction by detection of electromagnetic flux.In the present embodiment, digital compass 4 is a magnetic field sensormade by Honeywell, Inc. Any of a number of different types ofcommercially available digital compasses can be used.

Referring now to FIG. 11, a schematic representation of a magnetic fieldsensor 1100 in accordance with one embodiment of the present inventionis shown. In this embodiment, magnetic field sensor 1100 is comprised,in part, of three sensors 1102, 1104, and 1106. By having three sensors,magnetic field sensor 1100 is able to determine the elevation angle ofintegrated position and direction system 100 of FIG. 1. Morespecifically, in one embodiment, sensors 1102 (x-direction sensor) and1104 (y-direction sensor) determine the azimuthal orientation ofintegrated position and direction system 100. However, the determinationof azimuthal orientation will determined with the assumption thatintegrated position and direction system 100 is held level. Thus, if,for example, a user of integrated position and direction system 100 iswalking up a steep hill; walking down a steep hill; holding theintegrated position and direction system 100 in a vertically orientedmanner; and the like, the accuracy of the determined azimuthalorientation may be severely compromised. By using magnetic field sensor1100 which includes sensor 1106 (z-direction sensor), the presentembodiment is able to correctly determine the azimuthal orientation ofintegrated position and direction system 100 by correcting for anyvariation from horizontal in the position of integrated position anddirection system 100. That is, sensor 1106 of the present embodimentdetermines the variance in integrated position and direction system 100from a truly horizontal position. It will be understood that in therepresentation of FIG. 11, when integrated position and direction system100 is at a truly horizontal position, sensor 1106 will be verticallyoriented. Although a specific schematic implementation is shown in FIG.11, the present invention is well suited to use with any of a number ofdifferent types of commercially available digital compasses whichcompensate for variations from a horizontal orientation.

Referring still to FIG. 11, in one embodiment, in addition to correctingthe determined azimuthal orientation of integrated position anddirection system 100 for variance from a truly horizontal orientation,the present invention also determines (and optionally displays) theelevation angle of integrated position and direction system 100. In suchan embodiment, the user is made aware not only of the accurate azimuthalorientation (i.e. the direction in which integrated position anddirection system 100 is pointed), but the user is also informed of theelevation angle at which integrated position and direction system 100 isoriented. Hence, the user can determine, for example, the slope of ahill by holding integrated position and direction system 100 parallel tothe surface of the hill and reading the determined elevation angle.Additionally, although magnetic field sensor 1100 is comprised, in part,of three orthogonally oriented sensors 1102, 1104, and 1106 in thepresent embodiment, the present invention is also well suited to anembodiment in which more than three sensors are used and to anembodiment in which the plurality of sensors are arranged other thanorthogonally.

FIG. 5 shows a method for indicating direction and heading according toone embodiment of the present invention. As shown by steps 501-502, whenthe SATPOS is moving, heading is determined using the SATPOS. In thepresent embodiment, a satellite positioning system including a receiveradapted to receive satellite position determining signals such as, forexample, SATPOS 3 of FIGS. 1-4 is used to both determine whether theSATPOS is moving and to determine heading.

In one embodiment of the present invention, the determination of whetherthe SATPOS is moving (step 501) is made by comparing the velocity ofmovement to a threshold velocity. In the present embodiment, priordeterminations of position are compared to the most recent determinationof position, along with the time of each determination of position todetermine the velocity of movement of the SATPOS. When the velocity isdetermined to be greater than the threshold velocity, the SATPOS isconsidered to be moving.

As shown by step 505 of FIG. 5, when the SATPOS is moving, heading isindicated using the heading determined in step 502. In the embodimentshown in FIG. 1, display device 2 is used to indicate heading; and inthe embodiment shown in FIGS. 2-3, display device 28 is used to indicateheading.

Still referring to FIG. 5, when the SATPOS is not moving, as shown bysteps 501 and 503, direction is determined using the digital compass. Inthe present embodiment digital compass 4 of FIGS. 1-4 is used fordetermining direction.

As shown by step 506 of FIG. 5, when the SATPOS is not moving, directionis indicated using the direction determined by the digital compass instep 503. In the embodiment shown in FIG. 1, display device 2 is used toindicate direction; and in the embodiment shown in FIGS. 2-3, displaydevice 28 is used to indicate direction.

The indications of direction and heading steps 505-506 can take any of anumber of different forms. In one embodiment, heading and direction areindicated using a displayed compass rose. That is, icons representing acompass rose are displayed on, for example, display device 2 of FIG. 1or display device 28 of FIGS. 2-3.

In one embodiment of the present invention the direction and headingindicated in steps 505-506 are indicated using a four-point compassrose. That is, direction is indicated relative to the compass points ofNorth(N.), South(S.), East(E.), and West(W.). FIGS. 6a-6 b showexemplary displays 600 a-600 b that include a four-point compass rosethat can be used to indicate either heading (step 505 of FIG. 5) ordirection (step 506 of FIG. 5).

Referring now to FIGS. 6a-6 b, in the present embodiment, an icon isused to indicate whether heading is being displayed or whether directionis being displayed. More particularly, in display 600 a of FIG. 6a, icon602 is displayed to indicate to the user that heading is beingdisplayed. Referring now to FIG. 6B, display 600 b indicates thatdirection is being displayed. That is, the absence of icon 602 of FIG.6A indicates that the digital compass is being used and that directionis being displayed.

In the embodiments shown in FIGS. 6A-6B, the compass rose is displayedsuch that direction and heading are indicated relative to alignment mark601. That is, the compass rose is rotated such that the proper directionor heading is always indicated by reference to alignment mark 601. Thus,in the embodiment shown in FIG. 6A, because the compass point of N. isaligned with alignment mark 601, display 600 a indicates that the SATPOShas a heading directly to the North. Similarly, in the embodiment shownin FIG. 6B, because the compass point of N is aligned with alignmentmark 601, display 600 b indicates a North direction. That is, the SATPOSis oriented such that alignment mark 601 is pointing directly to theNorth.

FIGS. 7A-7B shown an embodiment in which direction and heading areindicated using an eight-point compass rose. That is, direction andheading are indicated relative to the compass points of North(N.),South(S.), East(E.), West(W.), North East(NE.), South East(SE.), SouthWest(SW.), and North West(NW.).

Referring now to FIGS. 7A-7B, exemplary displays 700 a and 700 b areshown to include an eight-point compass rose that can be used toindicate either heading (step 505 of FIG. 5) or direction (step 506 ofFIG. 5). As in the embodiment shown in FIGS. 6A-6B, direction andheading are indicated relative to alignment mark 601 and icon 602indicates whether direction or heading is being displayed.

In the embodiment shown in FIG. 7A, because the compass point of E isaligned with alignment mark 601, and because icon 602 is displayed,display 700 a indicates that the SATPOS has a heading directly to theEast. Similarly, in the embodiment shown in FIG. 7B, because the compasspoint of E is aligned with alignment mark 601, and because icon 602 isnot displayed, display 700 b indicates a East direction. That is, theSATPOS is oriented such that the top of the display, as indicated byalignment mark 601, is pointing directly to the East.

FIGS. 8A-8B show an embodiment in which both a four point compass roseand an eight-point compass rose are used. In the present embodiment, thedisplay of a four-point compass rose indicates that heading (step 505 ofFIG. 5) is being displayed while the display of an eight-point compassrose indicates that direction (step 506 of FIG. 5) is being displayed.In the embodiment shown in FIGS. 8A-8B, direction and heading areindicated relative to the top of the display, as indicated by alignmentmark 601. It should be understood that the compass rose can beimplemented with any number of points (e.g., a 16-point compass rose,etc.).

Now referring to display 800 a of FIG. 8A, because the compass point ofE is aligned with alignment mark 601, and because a four-point compassrose is displayed, display 800 a indicates that the SATPOS has a headingdirectly to the East. Similarly, in the embodiment shown in FIG. 8B,because the compass point of E is aligned with alignment mark 601, andbecause an eight-point compass rose is displayed, display 800 bindicates a East direction. That is, the SATPOS is oriented such thatthe top of the display, as indicated by alignment mark 601 is pointingin the cardinal direction of East.

The apparatus and method of the present invention automatically switchesbetween displays of heading and direction as the SATPOS moves and stopsmoving. Thus, the method and apparatus of the present invention providean uninterrupted display that can be used to find features, waypoints,etc. In the present embodiment, either heading or direction iscontinually displayed.

In the present embodiment, the determined position is also indicated. Inthe embodiment shown in FIGS. 6A-8B, position is indicatedalphanumerically using latitude and longitude as shown by icon 610.Alternatively, position is indicated by an icon displayed on a movingmap display.

In one embodiment of the present invention, position, direction andheading are indicated using a moving map display. FIGS. 9A-9B shows anexemplary display 900 that includes position icon 920 that indicates theposition of the SATPOS relative to icons 910-912 that representfeatures. In the present embodiment, icon 910 indicates the position ofa feature that is a fire hydrant, icon 911 indicates the position of afeature that is a tree, and icon 912 indicates the position of a featurethat is a building.

Referring now to FIGS. 9A-9B, exemplary displays 900 a and 900 b areshown to include position icon 920 that indicates the position of theSATPOS relative to features 910-912. As in the embodiment shown in FIGS.6A-7B, an icon 602 is displayed to indicate whether direction or headingis being displayed. In the present embodiment, an icon 921 thatindicates the direction of North is also displayed so that the user candetermine the orientation of the moving map display.

Referring now to FIG. 9A, an exemplary display 900 a is shown thatindicates a heading of North. That is, because heading icon 602 isdisplayed, a display of heading is indicated (step 505 of FIG. 5).Because the map is oriented such that the North icon is pointed to thetop of the display, the heading is indicated as being directly to theNorth.

Referring now to FIG. 9B, an exemplary display 900 b is shown thatindicates a direction of West. That is, because heading icon 602 is notdisplayed, a display of direction is indicated (step 506 of FIG. 5).Because the map is oriented such that the North icon is pointed to theright side of the display, the direction is indicated as being directlyto the West. That is, the display is oriented such that the top of thedisplay points in the cardinal direction of West.

The apparatus and method of the present invention automatically switchesbetween displays of heading and direction as the SATPOS moves and stopsmoving. Thus, the method and apparatus of the present invention providean uninterrupted display that can be used to find features such as, forexample, features 910-912 of displays 900 a-900 b.

The present invention is well adapted for other indications of headingand direction other than those shown in FIGS. 6A-9B. In one embodiment,heading and/or direction are indicated using an indication of degreesfrom 0 to 360 degrees. That is, a number is displayed on the displaydevice that indicates cardinal direction with 0 and 360 being North.That is, in the embodiment shown in FIG. 1, display device 2 displays anumber from 0 to 360; and in the embodiment shown in FIGS. 2-3, displaydevice 28 displays a number from 0 to 360.

The embodiments shown in FIGS. 1-9B of the present invention provide amethod and apparatus for providing an accurate indication of directionand heading to a user of a SATPOS device. When the user is stationary,position is accurately indicated using a digital compass. When the useris moving, the direction of movement(heading) is accurately indicated.Because the integrated position and direction system of the presentinvention always indicates either heading or direction, the user isalways able to locate features, waypoints, etc.

Prior art digital compasses are typically calibrated manually byrotating the digital compass in a circular arc. The digital compass ofthe present invention can be manually calibrated using this technique.

In one embodiment of the present invention the digital compass isautomatically calibrated using the SATPOS determination of heading. Inone embodiment of the present invention, the digital compass isautomatically calibrated upon selection of an icon or button thatindicates “Automatic Compass Calibration” when the position anddirection system of the present invention is moving (e.g. when step 501of FIG. 5 indicates that the SATPOS is moving).

In one embodiment of the present invention, the digital compass isautomatically calibrated on a periodic basis, without any required inputfrom the operator, when the SATPOS is moving. In one embodiment, thedigital compass is automatically calibrated according to user selectabletime periods. In the present embodiment, the user can select timeperiods of ten minutes, 30 minutes, one hour, four hours, or 12 hours.Thus, for example, when a user selects a time period of ten minutes, thedigital compass is calibrated when the digital compass begins to moveand every ten minutes thereafter until the digital compass stops moving.This provides for easily maintaining the accuracy of the digitalcompass.

In the present embodiment, the digital compass is calibrated bydetermining heading using the SATPOS, and adjusting the directionindicated by the digital compass according to the heading determined bythe satellite positioning system. In the embodiment shown in FIG. 1,controller 1 is operable to automatically calibrate the digital compass;in the embodiment shown in FIGS. 2-3, direction program 22 is operableto automatically calibrate the digital compass; and in the embodimentshown in FIG. 4, direction program 42 is operable to automaticallycalibrate the digital compass.

FIG. 10 shows a method for calibrating a digital compass 1000 in which adigital compass (e.g. digital compass 4 of FIGS. 1-4)is calibrated usinga heading determined using a SATPOS (e.g., SATPOS 3 of FIGS. 1-4).Referring now to step 501 a the velocity determined by the SATPOS iscompared to a threshold velocity. If the velocity is not greater thanthe threshold velocity (steps 501 a and 503), direction is determinedusing the digital compass(step 503), and direction is indicated as shownby step 506.

Continuing with FIG. 10, if the velocity is not greater than thethreshold velocity, heading is determined using the SATPOS as shown bysteps 501 a and 502. The heading determined using the SATPOS is thenindicated as shown by step 505.

Still referring to FIG. 10, as shown by step 550, the heading indicatedby the digital compass is determined. In the embodiment shown in FIG. 1,controller 1 is operable to determine the heading indicated by thedigital compass using input from digital compass 4; in the embodimentshown in FIGS. 2-3, direction program 22 is operable to determine theheading indicated by the digital compass; and in the embodiment shown inFIG. 4, direction program 42 is operable to determine the headingindicated by the digital compass.

The heading indicated by the digital compass is then compared to theheading determined using the SATPOS as shown by step 550. If thedifference between the heading determined using the SATPOS and theheading indicated by the digital compass by more than a predeterminederror threshold, the digital compass is calibrated as shown by steps550-551. In one embodiment, a default error threshold of between one totwo percent is initially used, which can be altered by the user at anytime to accommodate the needs of that particular user. The presentembodiment allows for the automatic calibration of the digital compasswhenever the heading indicated by the digital compass significantlyvaries from the heading determined using the SATPOS.

As discussed above, the present invention provides for automaticallycalibrating a digital compass, either as a result of user input (e.g.,selection of an icon, pressing of a button, etc.), or as a result ofuser-defined criteria for automatic calibration. That is, the user canprogram the present invention to automatically calibrate the digitalcompass (e.g. when velocity exceeds a given threshold, whenever theSATPOS begins moving, periodically while the SATPOS is moving, when thedifference between the SATPOS determined heading differs from theheading indicated by the digital compass by more than a predeterminedthreshold, etc. The integrated position and direction system of thepresent invention is easy to use since there in no need for a user tomanually calibrate the digital compass.

Though the embodiments shown in FIGS. 1-9B describe the indication ofeither direction or heading, the present invention is well adapted fordisplay of both direction and heading when the SATPOS is moving.

FIG. 12 is a perspective view of an integrated position and directionsystem 100 in accordance with an embodiment of the present inventionthat includes a visual alignment mechanism 90. The integrated positionand direction system 100 also includes a compact housing 30 which ispalm-size and a display device 28. Moreover, the integrated position anddirection system 100 has function keys/buttons 32 and alphanumerickeypad/buttons 33 to enable a user to provide user input to theintegrated position and direction system 100. It should be understoodthat the integrated position and direction system 100 can be configuredin any other manner and can include other components.

In one embodiment, the visual alignment mechanism 90 is a line on thetop surface of the integrated position and direction system 100. Inanother embodiment, the visual alignment mechanism 90 is a raisedsurface extending from the top surface of the integrated position anddirection system 100. In an alternate embodiment, the visual alignmentmechanism 90 is an icon or other visible indicia displayed on thedisplay device 28.

The integrated position and direction system 100 includes a user inputdevice for coupling user input to the integrated position and directionsystem 100. In an embodiment, the user utilizes the user input device tointeract with information displayed on the display device 28. In oneembodiment, a button of the function keys/buttons 32 is used as a userinput device. In another embodiment, a button of the alphanumerickeypad/buttons 33 is used as a user input device. In an alternateembodiment, the user input device includes a graphical user interface.It should be understood that any number of other methods can be used forcoupling user input to the integrated position and direction system 100.

In one embodiment, the integrated position and direction system 100determines the position of an offset feature. The term “offset feature”as used herein includes anything that is located at a position otherthan the position or positions of the integrated position and directionsystem 100. Examples of offset features include natural features such astrees, rocks, plants, etc., and manmade features such as buildings,telephones poles, fire hydrant, etc. Additionally, offset features caninclude animals, persons, and all types of inanimate objects. Theintegrated position and direction system 100 has a satellite positionsystem 3 (SATPOS) and a digital compass 4, as described above.

According to one embodiment of the present invention, the position of anoffset feature is determined without physically placing the integratedposition and direction system 100 at the location of the offset feature.Thus, if the offset feature is inaccessible for any reason or if it isinconvenient to place the integrated position and direction system 100at the location of the offset feature, the position of the offsetfeature can still be determined by employing the method and apparatus ofthe present invention.

Moreover, by utilizing no more than the integrated position anddirection system 100 which is compact and palm-sized, the position ofthe offset feature is determined, eliminating the need to carry aroundunwieldy equipment or to set up extensive measuring apparatus to obtainthe position of the offset feature. In other words, the integratedposition and direction system 100 provides a self-contained, portableapparatus to determine the position of the offset feature in a fast,efficient, and convenient manner.

FIG. 13 is a flow chart illustrating a method 1500 of determiningposition of an offset feature in accordance with an embodiment of thepresent invention. Reference is made to FIG. 14. The steps of method1500 are hereafter illustrated with reference to exemplary offsetfeature 930 of FIG. 14 and exemplary locations L1 and L2 of FIG. 14.

At step 1505, the method of determining position of the offset feature930 in accordance with an embodiment of the present invention begins.

As shown in FIG. 14, the offset feature 930 is made inaccessible by theriver 935. The position of the offset feature 930 is determined byutilizing the integrated position and direction system 100 of thepresent invention. It should be understood that the first location L1and the second location L2 can be located differently than shown in FIG.14.

At step 1510, the integrated position and direction system 100 of thepresent invention is moved and placed at the first location L1 relativeto the location of the offset feature 930. The integrated position anddirection system 100 is compact and palm-sized such that a user caneasily move the integrated position and direction system 100 to thefirst location L1. The first location L1 can be any location that isconvenient to the user.

At step 1515, the visual alignment mechanism 90 of the integratedposition and direction system 100 is aligned with the offset feature930.

At step 1520, the user initiates the integrated position and directionsystem 100 to determine the first set of measurements. In particular,the user operates the integrated position and direction system 100 via auser input device (e.g., by pressing a button of FIG. 12 or by operatinga graphical user interface of FIG. 17) to determine the first set ofmeasurements while the integrated position and direction system 100 isaligned with the offset feature 930.

Referring now to step 1525, the integrated position and direction system100 determines a first direction to the offset feature 930 and a firstposition of the integrated position and direction system 100. The firstdirection is determined using the digital compass 4. The first positionis determined using the satellite positioning system 3 (SATPOS). Theintegrated position and direction system 100 stores the first set ofmeasurements. Alternatively, a first heading is determined using theSATPOS 3 rather than determining the first direction to the offsetfeature using the digital compass 4.

As shown by step 1530, the integrated position and direction system 100of the present invention is move and placed at the second location L2.The second location L2 can be any location that is convenient to theuser. The greater the distance between the first location L1 and thesecond location L2 the more accurate the computed position of the offsetfeature can be.

With reference to step 1535, the visual alignment mechanism 90 of theintegrated position and direction system 100 is again aligned with theoffset feature 930. This alignment affects the accuracy of thecalculated position of the offset feature 930.

As shown by step 1540, the user again initiates the integrated positionand direction system 100 to determine the second set of measurements. Inparticular, the user operates the integrated position and directionsystem 100 via a user input device (e.g., by pressing a button of FIG.12 or by operating a graphical user interface of FIG. 17) to determinethe second set of measurements.

Referring to step 1545, the integrated position and direction system 100determines a second direction to the offset feature 930 and a secondposition of the integrated position and direction system 100. The seconddirection is determined using the digital compass 4. The second positionis determined using the satellite positioning system 3 (SATPOS). Theintegrated position and direction system 100 stores the second set ofmeasurements. Alternatively, a second heading is determined using theSATPOS 3 rather than determining the second direction to the offsetfeature using the digital compass 4.

As shown by step 1550, the integrated position and direction system 100calculates the position of the offset feature 930 using the stored firstand second sets of measurements (i.e., the first and second directionsand the first and second positions). In the present embodiment, thecalculated position of the offset feature 930 is displayed on displaydevice 28.

At step 1555, the method in accordance with an embodiment of the presentinvention ends.

FIG. 14 shows an exemplary diagram in which an integrated position anddirection system is located at a first location (L1) and subsequentlylocated at a second location (L2) for determining the location of offsetfeature 930. In the embodiment shown in FIG. 14, the offset feature 930is made inaccessible by the river 935. The position of the offsetfeature 930 is determined by utilizing the integrated position anddirection system 100 of the present invention. It should be understoodthat the first location L1 and the second location L2 can be locateddifferently than shown in FIG. 14. It should be understood that the2-dimensional position or the 3-dimensional position of the offsetfeature 930 can be determined by using the integrated position anddirection system 100.

FIG. 14 illustrates that the first location L1, the second location L2,and the location of the offset feature 930 form a triangle 950. Thetriangle 950 has a side A which is the distance between the location ofthe offset feature 930 and the second location L2, a side E which is thedistance between the second location L2 and the first location L1, and aside B which is the distance between the first location L1 and thelocation of the offset feature 930. In addition, the triangle 950 has anangle a centered at the first location L1, an angle b centered at thesecond location L2, and an angle e centered at the location of theoffset feature 930.

In practice, the first and second sets of measurements (gathered at thefirst location L1 and the second location L2, respectively) enable theintegrated position and direction system 100 to compute the angle a, theangle b, and the side E of the triangle 950. Then, the integratedposition and direction system 100 employs trigonometric identities andprinciples to calculate angle e, side B, and side A of the triangle 950.Since the first and second positions of the first and second locationsL1 and L2 have been determined by the SATPOS 3, the integrated positionand direction system 100 can determine the position of the offsetfeature 930 by using the distance B (in the direction to the offsetfeature measured at the first location L1) in a series of furthertrigonometric calculations based upon a local grid forlatitude-longitude (or other X-Y coordinate system) in which the twoknown points are first laid out, and the position of the offset feature930 is determined in relation to these known coordinates. Hence, theposition of the offset feature 930 is determined using only theintegrated position and direction system 100 which has the digitalcompass 4 and the SATPOS 3.

FIGS. 15A-15G illustrate exemplary angles and distances that can be usedto calculate the position of the offset feature 930 in accordance withan embodiment of the present invention.

FIG. 15A illustrates the triangle 950 of FIG. 14. Using the firstposition (measured at the first location L1) and the second position(measured at the second location L2), the integrated position anddirection system 100 calculates the distance E.

FIG. 15B illustrates that the first direction measured at the firstlocation L1 by the digital compass 4 represents an angle Q measured fromthe reference meridian R to the location of the offset feature 930.

FIG. 15C illustrates that a direction to the second location L2(relative to the first location L1) represented by the angle K (measuredfrom the reference meridian R to the second location L2) can bedetermined from the first and second positions measured by the SATPOS 3.

FIG. 15D illustrates that the angle a of the triangle 950 can bedetermined by taking the absolute value of the difference between angleK and angle Q.

FIG. 15E illustrates that the second direction measured at the secondlocation L2 by the digital compass 4 represents an angle N measured fromthe reference meridian R to the location of the offset feature 930.

FIG. 15F illustrates that a direction to the first location L1 (relativeto the second location L2) represented by the angle M (measured from thereference meridian R to the first location L1) can be determined fromthe first and second positions measured by the SATPOS 3.

FIG. 15G illustrates that the angle b of the triangle 950 can bedetermined by taking the absolute value of the difference between angleM and angle N.

Referring again to FIG. 15A, once angle a and angle b are determined,the integrated position and direction system 100 can use a trigonometricidentity to compute angle e. In particular, the angles of the triangle950 produce the sum 180 degrees. Hence, the angle e has the valueresulting from 180 degrees minus the angle a and minus the angle b.

Moreover, since the angle a, the angle b, the angle e, and the distanceE are now known, the law of sines is utilized to determine the distanceB and the distance A of the triangle 950. The law of sines states:

(sin a)/A=(sin e)/E  (eq.1)

(sin b)/B=(sin e)/E.  (eq.2)

In particular, equation 1 is used to determine distance A. Moreover,equation 2 is used to determine distance B.

In one embodiment, the integrated position and direction system 100incorporates 1) the first direction and 2) the distance B, to the firstposition measured by the SATPOS 3 at the first location L1 to computethe position of the offset feature 930. In another embodiment, theintegrated position and direction system 100 incorporates 1) the seconddirection and 2) the distance A, to the second position measured by theSATPOS 3 at the second location L2 to compute the position of the offsetfeature 930. It should be understood that the position of the offsetfeature 930 can be calculated from the first and second sets ofmeasurements using any of a number of other different methods.

Though method 1500 of FIG. 13 shows the calculation of the position ofan offset feature using only two locations (L1 and L2), the presentinvention can use more locations for more accurately determining thelocation of an offset feature.

FIG. 16 shows an exemplary diagram in which an integrated position anddirection system is located at a first location (L1) and subsequentlylocated at a second location (L2) and subsequently moved to a thirdlocation (L3) for determining the location of offset feature. In oneembodiment, the integrated position and direction system 100 is movedand placed at a third location L3 and a third set of measurements aredetermined using the digital compass 4 and the SATPOS 3, as describedabove. The first triangle formed by the first location L1, the secondlocation L2, and the location of the offset feature is used to obtain afirst computed position of the offset feature. The second triangleformed by the first location L1, the third location L3, and the locationof the offset feature is used to obtain a second computed position ofthe offset feature. It should be understood that the integrated positionand direction system 100 can be placed at more than three locationsrelative to the location of the offset feature.

In one embodiment, the integrated position and direction system 100verifies the accuracy of the computed position of the offset feature bychecking that the difference between the first and second computedpositions of the offset feature is within a threshold level. Thethreshold level can be set to any value by the user. In anotherembodiment, if the difference is not within the threshold value, theintegrated position and direction system 100 prompts the user to restartthe procedure (illustrated in FIG. 13) for determining the position ofthe offset feature.

In another embodiment, the integrated position and direction system 100computes the average of the first computed position of the offsetfeature and the second computed position of the offset feature, whereasthe average of these computed positions is designated as the position ofthe offset feature.

FIG. 17 illustrates an embodiment that includes a graphical userinterface that is used for determining the position of an offsetfeature. In one embodiment, the user input device is a graphical userinterface displayed on the display screen of display device 28. In oneembodiment, the graphical user interface includes instructions 98 foroperating the integrated position and direction system 100 to determinethe position of the offset feature. Moreover, the graphical userinterface includes a plurality of displayed data 93 representing thecalculated position of the offset feature and the sets of measurementsobtained at the plurality of locations.

In addition, the graphical user interface includes a first icon 95 and asecond icon 96, whereas the user invokes the appropriate icon to causethe integrated position and direction system 100 to determine thedirection to the offset feature and to determine the position of theintegrated position and direction system 100, at the respectivelocations. It should be understood that the first icon 95 and the secondicon 96 can also be implemented as menu items or using any number ofuser interface devices. As described above, the user aligns the visualalignment mechanism 90 with the offset feature before causing theintegrated position and direction system 100 to determine the set ofmeasurements at each location. It should be understood that thegraphical user interface can be configured in any of a number of othermanners. Other embodiments of the graphical user interface allow theuser to place the integrated position and direction system 100 at morethan two locations for determining the location of an offset feature.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

What is claimed is:
 1. A method of determining a position of an offsetfeature using an integrated position and direction system (IPADS) havinga satellite positioning system and a digital compass, said methodcomprising the steps of: a) aligning said IPADS relative to said offsetfeature at a first location; b) determining a first set of measurementsat said first location by using said satellite positioning system andsaid digital compass; c) aligning said IPADS relative to said offsetfeature at a second location; d) determining a second set ofmeasurements at said second location by using said satellite positioningsystem and said digital compass; and e) using said first and second setsof measurements to calculate said position of said offset feature.
 2. Amethod as recited in claim 1 wherein said IPADS includes a visualalignment mechanism, and wherein said step a) includes aligning saidalignment mechanism with said offset feature.
 3. A method as recited inclaim 2 wherein said step c) includes aligning said visual alignmentmechanism with said offset feature.
 4. A method as recited in claim 3wherein said visual alignment mechanism comprises a line on a topsurface of said IPADS.
 5. A method as recited in claim 3 wherein saidvisual alignment mechanism comprises a raised surface extending from atop surface of said IPADS.
 6. A method as recited in claim 1 whereinsaid first set of measurements includes a first direction indicatingorientation of said offset feature relative to said first location,wherein said second set of measurements includes a second directionindicating orientation of said offset feature relative to said secondlocation, wherein said first direction and said second direction aredetermined by using said digital compass.
 7. A method as recited inclaim 1 wherein said first set of measurements includes a first positiondetermined by using said satellite positioning system, and wherein saidsecond set of measurements includes a second position determined byusing said satellite positioning system.
 8. A method as recited in claim1 wherein said IPADS includes a user input device for allowing a user tooperate said IPADS to determine said position of said offset feature,wherein said step b) is initiated by operation of said user inputdevice, and wherein said step d) is initiated by operation of said userinput device.
 9. A method as recited in claim 8 wherein said user inputdevice comprises a button.
 10. A method as recited in claim 8 whereinsaid user input device comprises a graphical user interface.
 11. Amethod as recited in claim 1 further comprising displaying said positionof said offset feature.
 12. A method as recited in claim 1 wherein saidstep e) further comprises the steps of: aligning said IPADS relative tosaid offset feature at a third location; determining a third set ofmeasurements at said third location using said satellite positioningsystem and said digital compass; and using said first, second and thirdsets of measurements to calculate said position of said offset feature.13. A method of determining a position of an offset feature using anintegrated position and direction system (IPADS) having a satellitepositioning system and a digital compass, said method comprising thesteps of: a) at a first location, determining a first position usingsaid satellite positioning system and determining a first direction tosaid offset feature using said digital compass; b) at a second location,determining a second position using said satellite positioning systemand determining a second direction to said offset feature using saiddigital compass; and c) calculating said position of said offset featureusing said first and second positions and said first and seconddirections.
 14. A method as recited in claim 13 wherein said IPADSincludes a visual alignment mechanism, and wherein said step a) includesaligning said alignment mechanism with said offset feature.
 15. A methodas recited in claim 14 wherein said step b) includes aligning saidvisual alignment mechanism with said offset feature.
 16. A method asrecited in claim 15 wherein said visual alignment mechanism comprises aline on a top surface of said IPADS.
 17. A method as recited in claim 15wherein said visual alignment mechanism comprises a raised surfaceextending from a top surface of said IPADS.
 18. A method as recited inclaim 13 wherein said IPADS includes a user input device for allowing auser to operate said IPADS to determine said position of said offsetfeature, wherein said step a) is initiated by operation of said userinput device, and wherein said step b) is initiated by operation of saiduser input device.
 19. A method as recited in claim 18 wherein said userinput device comprises a button.
 20. A method as recited in claim 18wherein said user input device comprises a graphical user interface. 21.A method as recited in claim 13 further comprising displaying saidposition of said offset feature.
 22. A method as recited in claim 13further comprising the steps of: d) at a third location, determining athird position using said satellite positioning system and determining athird direction to an offset feature using said digital compass; and e)using said positions of steps a), b) and d) and said directions of stepsa), b), and d) to calculate said position of said offset feature.
 23. Anintegrated position and direction system (IPADS) for determining theposition of an offset feature, comprising: a) a satellite positioningsystem (SPS) for determining a plurality of positions using satelliteposition determining signals; b) a digital compass for determining aplurality of directions; c) a user input device for receiving userinput; and d) a processor coupled to said SPS, coupled to said digitalcompass, and coupled to said user input device, wherein said processoris operable in response to operation of said user input device todetermine said position of said offset feature using said positions andsaid directions.
 24. An integrated position and direction system asrecited in claim 23 wherein said user input device comprises a button.25. An integrated position and direction system as recited in claim 23wherein said user input device comprises a graphical user interface. 26.An integrated position and direction system as recited in claim 23wherein said satellite positioning system uses satellites of the U.S.Global Positioning System to determine said positions.
 27. An integratedposition and direction system as recited in claim 23 wherein saiddigital compass includes at least three sensors.
 28. An integratedposition and direction system as recited in claim 23 further comprisinga housing, said SPS, said digital compass, and said processor disposedin said housing.
 29. An integrated position and direction system asrecited in claim 28 wherein said housing is palm-sized.
 30. Anintegrated position and direction system as recited in claim 28 furthercomprising a visual alignment mechanism for facilitating aligning saidIPADS with said offset feature.
 31. An integrated position and directionsystem as recited in claim 30 wherein said visual alignment mechanismcomprises a line on a top surface of said housing.
 32. An integratedposition and direction system as recited in claim 30 wherein said visualalignment mechanism comprises a raised surface extending from a topsurface of said housing.